Rainier Arms Back Up Iron Sights (BUIS)


Back Up Iron Sights for AR type rifles, also known as BUIS, have been around for a while now. I remember getting my first folding rear BUIS by Knights Armament back in the late 90s in the first SOPMOD kit issued for my M4. Pretty simple concept really. A flat, folding, rudimentary sight to be used if the primary optic fails. The KAC offering I first had was basically a flat bar, with a peep sight. There was a plastic insert (that always got lost) to provide the shooter with a smaller peep for more precise shooting and a windage knob. It sat behind and under my Trijicon ACOG and never got used.

Fast forward 15 years or so and the BUIS is alive and well. Ironically, there is some debate regarding the necessity of the BUIS. Some will argue that with the advancement in optics the likelihood of optical failure is so minimal that the BUIS isn’t necessary. Others would say two is one and one is none. I fall into the second camp. I know money can be tight and good glass costs good coin, however I would recommend the BUIS be purchased first then the optic. I have a lot of rifles sans optics but I try to get a BUIS for every rifle. The optics will follow later when funds allow. Just my opinion.

"Ironically, there is some debate regarding the necessity of the BUIS."

There are many brands and styles to choose from and I have gone through many in my day. I recently received a set of the brand new BUIS from Rainier Arms. The Rainier Arms offering is pretty slick. It is one of the more low profile sights I have used. It only measures .35" tall when in the folded position. This allows the BUIS to fit snuggly under optics mounted low on the rifle. It is currently available only as a set and can be had in black or tan with the Rainier Arms logo boldly emblazoned on the front of each sight. Rainier has these made in Germany and their engineering heritage can be seen in the construction and design of the sights. The sights are made of a combination of steel and aluminum resulting in a very light weight package.

The BUIS appear to be robust. They are easily folded or put into battery with an audible click. It should be noted they do not lock into place meaning they are easily folded down and stowed without having to disengage a locking bar or other mechanism. There are differing opinions regarding BUIS that lock or those that don’t. Locking BUIS keep them in battery and always ready even when impacted. Some would argue this also increases the chance of them breaking if impacted. Unlocked BUIS can be knocked down if impacted eliminating potential snapage of said BUIS. They will then need to be manually returned to battery. Personally, I prefer a locking BUIS or ones that are held in place by spring pressure. The latter, if knocked down will spring back into place after the impact. Regardless, Rainier went with the unlocking variety.

The front sight is easily deployed, takes standard AR15 front sight posts as well as aftermarket posts like those offered from Blitzkrieg Components. Unlike traditional AR front sight posts, the Rainier Arms design allows the user to adjust the elevation without tools. Well, you do need your thumb and forefinger. The front post is protected by a pair of flared wings. These wings have cut outs on the sides that provide for a decent gripping surface for deployment.

The rear sight is pretty awesome. Similar to my old KAC BUIS the Rainier version provides a large ghost ring peep as well as a smaller peep. The difference is both options are integral to the BUIS. No insert to get lost. Not new to the modern BUIS game but nice. What sets them apart from a lot of leading manufactures of BUIS is that regardless of what peep is deployed the BUIS will still fold flat. When the small peep is not needed it can be folded down into the main structure of the BUIS. If needed it easily can be folded back up. Each position will issue an audible "click" thanks to an assumed, unseen spring assisted detent. The windage knob is easily manipulated on the right side of the sight. The positions are very positive and there are alignment hash marks engraved on the top of the sight housing that will give the shooter a visual indication of the windage adjustment.

Rainier Arms has done a very nice job incorporating form and function. These sights would fall in the premium BUIS category and for $249.95 they may not be for everyone. That being said, you get what you pay for and the combination of Rainier Arms and German craftsmanship deserves recognition. I truly hope they will offer a 45 degree offset option and/or a spring loaded or lockable version in the future. But for now I am very happy with the current offering. I plan to get some tan sights in the future as well. If you are in the market for a high quality, low profile back up iron sight for your AR build, take the time to check out the Rainier Arms offering. It may be just what the doctor ordered.

Check out Rainier Arms at Rainier Arms, on Facebook, and on Instagram.

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